98 lines
5.2 KiB
Plaintext
98 lines
5.2 KiB
Plaintext
psimpl - generic n-dimensional polyline simplification
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Copyright (C) 2010-2011 Elmar de Koning, edekoning@gmail.com
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--------------------------------------------------------------------------------
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28-09-2010 - Initial version
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23-10-2010 - Changed license from CPOL to MPL
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26-10-2010 - Clarified input (type) requirements, and changed the
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behavior of the algorithms under invalid input.
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01-12-2010 - Added the nth point, perpendicular distance and Reumann-Witkam
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routines; moved all functions related to distance calculations to
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the math namespace
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10-12-2010 - Fixed a bug in the perpendicular distance routine
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27-02-2011 - Added Opheim simplification, and functions for computing positional
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errors due to simplification; renamed simplify_douglas_peucker_alt
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to simplify_douglas_peucker_n
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18-06-2011 Added Lang simplification; fixed divide by zero bug when using
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integers; fixed a bug where incorrect output iterators were
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returned under invalid input; fixed a bug in douglas_peucker_n
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where an incorrect number of points could be returned; fixed a bug
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in compute_positional_errors2 that required the output and input
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iterator types to be the same; fixed a bug in
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compute_positional_error_statistics where invalid statistics could
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be returned under questionable input; documented input iterator
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requirements for each algorithm; miscellaneous refactoring of most
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algorithms.
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--------------------------------------------------------------------------------
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'psimpl' is licensed under the Mozilla Public License Version 1.1 (MPL), see
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the accompanying LICENSE.txt file. Alternatively a copy of this license may be
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obtained from http://www.mozilla.org/MPL/.
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--------------------------------------------------------------------------------
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'psimpl' is hosted at SourceForge: http://sourceforge.net/projects/psimpl/ and
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has a dedicated website: http://psimpl.sf.net
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Originally psimpl was released as part of the article 'Polyline Simplification'
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at The Code Project:
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http://www.codeproject.com/KB/recipes/PolylineSimplification.aspx
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================================================================================
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'psimpl' is a c++ polyline simplification library that is generic, easy to use,
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and supports the following algorithms:
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Simplification
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* Nth point - A naive algorithm that keeps only each nth point
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* Distance between points - Removes successive points that are clustered
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together
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* Perpendicular distance - Removes points based on their distance to the line
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segment defined by their left and right neighbors
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* Reumann-Witkam - Shifts a strip along the polyline and removes points that
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fall outside
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* Opheim - A constrained version of Reumann-Witkam
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* Lang - Similar to the Perpendicular distance routine, but instead of looking
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only at direct neighbors, an entire search region is processed
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* Douglas-Peucker - A classic simplification algorithm that provides an
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excellent approximation of the original line
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* A variation on the Douglas-Peucker algorithm - Slower, but yields better
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results at lower resolutions
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Errors
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* positional error - Distance of each polyline point to its simplification
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All the algorithms have been implemented in a single standalone C++ header
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using an STL-style interface that operates on input and output iterators.
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Polylines can be of any dimension, and defined using floating point or signed
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integer data types.
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================================================================================
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The demo package contains a win32 demo application for 'psimpl'. The demo
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application allows you to experiment with the different simplification
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algorithms. It can generate pseudo random 2D-polylines of up to 10.000.000
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vertices in various types of containers. The boundingbox of the generated
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polyline is always 2n x n, where n is the amount of vertices of the generated
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polyline. Use this fact to specify a proper distance tolerance.
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Internally, the generated and simplified polyline are always stored in a
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QVector<double>. Just before simplification, it is converted to the selected
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container type. Afterwards, this temporary container is destructed. Normally you
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won't notice this, but it seems that creating and destructing a
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std::list(10.000.000) can take a rather long time. The resulting performance
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measurements never include these conversion steps. I chose this approach as it
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allowed me to quickly add new container types.
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Note that the entire application is single threaded (sorry for being lazy),
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meaning it could go 'not responding' during a long running simplification.
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The demo application was made using Qt 4.7.3, Qt Creator 2.1.0 and Visual Studio
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2008 Express. Complete source code is included.
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================================================================================
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If you decide to use my code for your (commercial) project, let me know! I would
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love to hear where my code ends up and why you chose to use it! If possible, a
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voluntary donation to my PayPal account (edekoning@gmail.com) would be much
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appreciated.
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Regards,
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Elmar de Koning
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edekoning@gmail.com
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